1. Field of the Invention
The present invention relates to a resist pattern thickening material which is applied over a resist pattern to be thickened and is capable of thickening the resist pattern to be thickened, and which can form a fine space pattern, exceeding exposure limits of light sources of existing exposure devices (“space pattern” is hereby defined as a hole, groove, recess, or any other empty space that is formed by a developed (removed) resist). The present invention also relates to a process for forming a resist pattern and a process for manufacturing a semiconductor device, all of which use the resist pattern thickening material.
2. Description of the Related Art
Semiconductor integrated circuits are becoming more highly integrated, and LSIs and VLSIs are being put into practical use. Accompanying this trend, the wiring patterns extend to regions of 0.2 μm or less, and the smallest patterns extend to regions of 0.1 μm or less. A lithographic technique is extremely important in forming fine wiring patterns. In the lithographic technique, a substrate to be processed on which a thin film is formed, is coated by a resist film, is selectively exposed, and thereafter, is developed so as to form a resist pattern. Dry etching is carried out by using the resist pattern as a mask, and thereafter, by removing the resist pattern, the desired pattern is obtained.
In forming a fine wiring pattern utilizing the lithographic technique, it is necessary to make the light source of the exposure device be a short wavelength, as well as newly developing resist materials which have high resolution and is suitable to the characteristics of the light source. However, in order to make a light source of an exposure device be a short wavelength, it is necessary to update the exposure device, which results in very high costs. Further, the development of new resist materials suitable for an exposure with light of short wavelength is not easy.
To overcome the above technical problems, there has been proposed a technique wherein a resist pattern formed of a resist material is formed and thickened by using a resist pattern thickening material capable of forming a fine space pattern. In the art, the resist pattern thickening material is sometimes referred to a resist swelling agent.
For instance, Japanese Patent Application Laid-Open (JP-A) No. 10-73927 disclose a technique which is called RELACS, and can form a fine space pattern by using KrF (krypton fluoride) excimer laser light (wavelength: 248 nm) which is deep ultraviolet light as the exposure light of a resist. In this technique, a resist pattern is formed by exposing a resist (a positive resist or a negative resist) by using a KrF (krypton fluoride) excimer laser light (wavelength: 248 nm) as the exposure light. Thereafter, by using a water-soluble resin composition, a coated film is provided so as to cover the resist pattern. The coated film and the resist pattern are made to interact at the interface thereof by using the residual acid within the material of the resist pattern, and the resist pattern is thickened. (Hereinafter, this thickening of the resist pattern will be referred to upon occasion as “swelling”.) In this way, the distance between the resist patterns is shortened, and a fine space pattern is formed.
However, in the case of RELACS, the KrF resist which is used strongly absorbs ArF excimer laser light, since the KrF resist is formed of an aromatic resin composition such as a novolak resin, naphthoquinonediazide resin or the like, and an aromatic ring contained therein allows KrF excimer laser light (wavelength: 248 nm) pass through but absorbs light having a shorter wavelength than the KrF excimer laser light, i.e., ArF excimer laser light (wavelength: 193 nm). Thus, the ArF excimer laser light cannot pass through the KrF resist. There is therefore the problem that ArF excimer laser light cannot be used as the exposure light. Moreover, there is a problem in the RELACS technique that the resist swelling agent is effective for thickening (swelling) the KrF resist but not for thickening (swelling) the ArF resist.
From the standpoint of forming a fine wiring pattern, it is desirable to be able to use light of a shorter wavelength than KrF excimer laser light, e.g., ArF excimer laser light, as the light source of the exposure device. In case x-ray or electron beam having a shorter wavelength than ArF excimer laser light is used as exposure light of the resist to form the pattern, however, it results in high cost and low productivity. Thus, the utilization of ArF excimer laser light is desired.
Accordingly, the current situation is that there has not yet been developed a technique which can use ArF excimer laser light as the light source of an exposure device during patterning, which can sufficiently thicken ArF resist pattern or the like that cannot be thickened by using a resist swelling agent used in the RELACS technique, and which can easily form a fine space pattern at low cost.
An object of the present invention is to provide a resist pattern thickening material, which can utilize ArF excimer laser light as exposure light during patterning; which, when applied over a resist pattern to be thickened, can efficiently thicken the resist pattern to be thickened, e.g., in form of line-space pattern, regardless of the size of the resist pattern to be thickened; and which is suited for forming a fine space pattern, exceeding exposure limits of light sources of existing exposure devices.
Another object of the present invention is to provide a process for forming a resist pattern which, during patterning a resist pattern to be thickened, can utilize, as is, light sources (such as ArF excimer laser light and the like) of existing exposure devices; which can efficiently thicken the resist pattern to be thickened, e.g., in form of line-space pattern, regardless of the size of resist pattern to be thickened; which has excellent mass productivity; and which can finely manufacture a space pattern at low cost and high productivity, exceeding the exposure limits of such light sources, regardless of the material or the size of the resist pattern to be thickened.
Yet another object of the present invention is to provide a process for manufacturing a semiconductor device which, by using a space pattern which has been formed to be fine, can form a fine pattern on a substrate which is an oxide film, a nitride film, or the like, and which can efficiently mass produce high-performance semiconductor devices having fine wiring and the like.